Webs having a release coating on one or both sides are a typical example of the use of the present invention. Such webs are applied, for example, to adhesive surfaces of pressure sensitive tapes, "stick on" tile, two-faced tapes, and numerous other articles having an adhesive surface to protect until actual use. It is found that extremely thin coatings in the order 0.0001 to 0.00001 of an inch will suffice, especially when the release agent is as effective as certain liquid silicone polymers now available. These relatively high cost materials are economical as release agents only if they can be applied in substantially thinner coatings than can be applied by conventional coating machinery. Moreover, as the cost of paper fiber and other web forming materials is significant in the preparation of protective webs, the machinery for applying such ultra thin coatings is desirably capable of forwarding light-weight low-strength webs through the coating operation without any tearing or scuffing of the webs.
A particular difficulty that arises in the application of extremely thin coatings to webs is the attainment of an essentially continuous coating free of open spots which expose the surface of the web. Many coating compositions are extremely difficult to apply in a very thin uniform layer without any discontinuity. On the other hand, there are coaters which can meter a very thin film but in the process aerate the film and thus cause the film to rupture during deposition on the web.